Techopedia explains Chat

Chat may be delivered through text, verbal, audio, visual or audio-visual (A/V) communication via the Internet. If conducted through a desktop, chat requires software that supports Internet Relay Chat (IRC) or an instant messenger application, where a central server manages chat communication between different end user clients.

There are also online chat services that require users to sign up with a valid email address. After signing up, a user may join a group chat room or send a private message to another individual. Online chat services have purpose-built chat interfaces that manage the entire communication processes.